Efficacy of a novel lectin-conjugate platinum nanoparticle (MdLec-PtNP) to protect Nile tilapia (Oreochromis niloticus) from Aeromonas hydrophila infection by injection, immersion and oral routes of administration.

Vaccination offers a potential solution for tilapia aquaculture in low-to-middle-income countries (LMICs), where infectious disease outbreaks in fish are a major challenge. Aeromonas hydrophila hold an important role in resulting threats in aquaculture industry. Our study evaluated a novel lectin-based glycovaccine for protecting Nile tilapia (Oreochromis niloticus) against Aeromonas hydrophila. The glycovaccine, combining lectin from Metapenaeus dobsoni (MdLec) and platinum nanoparticles (PtNP) with formalin-inactivated A. hydrophila, was administered via injection, immersion and oral routes with a booster dose at 21 days post-vaccination. ELISA results showed significantly higher serum IgM levels in the injection group (p < 0.05) when compared to immersion and oral vaccinated groups. Histopathology revealed immune responses in gill and gut tissues, while RT-qPCR indicated increased expression of immune-related genes in the spleen and head kidney of MdLec-PtNP-A.hydrophila vaccinated fish (p < 0.05). Following the A. hydrophila challenge, the group injected with the MdLec-PtNP-A.hydrophila vaccine showed a relative percentage survival (RPS) of 79.6%. An RPS of 61.2% and 55.1% was observed in the groups that received the MdLec-PtNP-A.hydrophila vaccine via immersion and oral routes, respectively. This novel lectin-conjugated PtNP vaccine appears promising for protecting farmed tilapia against A. hydrophila, generating an effective protective immune response against the bacterium. The findings highlight the immunostimulatory properties of the nanoparticle and suggest that the MdLec-PtNP-A.hydrophila vaccine is a practical vaccination strategy for LMICs. Further studies are needed to test vaccine efficacy against more virulent strains of A. hydrophila and to investigate potential commercialization of the vaccine.